The operation of a ship lock, often in a canal system, connecting two bodies of water at different water levels requires alternate draining and refilling the water in the ship lock. The operation of an underground hydroelectric pumped-storage unit also requires alternate draining and refilling the water in two reservoirs separated by a difference in elevation. During the transfer of water, the unit has the capability for generating hydroelectric energy and for consuming and storing energy. This invention combines portions of the ship lock functions with those of the underground hydroelectric pumped-storage facility.